Magnesium alloy



Patented Dec. 31, 1940 1 UNITED STATES PATENT OFFICE MAGNESIUM ALLOY Arthur Burkhardt, Berlin-Iichterfelde, and Richard Knabe, Berlin-Zehlendori, Germany, assignols to Georg Von Gicsches Erben, Breslau, Germany, a corporation of Germany No Drawing. Application September 3, 1938, Serial No.- 228,324 In Germany September 21, 1937 2 Claims.

magnesium alloy of the class aforesaid, with a view to increasing its strength without deteriorating its resistance to corrosion.

Poor resistance to corrosion is one of the'principal disadvantages of magnesium alloys as known heretofore. If the resistance to corrosion is satisfactory, the strength of the alloy is of the order of only 30 kilogrammes per squaremillimeter. The strength can be increased by heat treatment but the resistance to corrosion is much reduced thereby. Another weakness of such heat treated alloys is that they are very sensitive to stress, and particularly'subjected to intercrystalline corrosion.

Under these conditions, it was impossible heretofore to make magnesium alloys possessing high strength and satisfactory resistance to corrosion.

It has been proposed to add manganese for increasing the corrosion resistance, but this ele-- ment' is very detrimental with respect to the mechanical properties, and especially to the toughness, of the alloys. Besides, it does not remove the high sensitivity to stress and the low resistance to intercrystalline corrosion present in such alloys.

By extensive investigations of magnesium alloysof the class containing aluminium, cadmium, and bismuth, we have made the surprising discovery that it is possible to produce magnesium alloys of the class aforesaid whose strength is far superior to that of the magnesium alloys known heretofore, without their corrosion resistance being affected.

The novel alloys according to our invention contain 1 to 15% aluminium, 1 to 15% cadmium,

and at least one metal of the group including bismuth, lead, and tin, the total oi the alloying elements being 6 to 23%.

The remainder of the alloys may be substantially all magnesium. The phase substantially all 'magnesium" is intended to include magnesium and magnesium with the usual impurities and minor amounts of alloying elements, generally not more than 0.1 'to 1%, as are common in technical magnesium. Such elements are, for instance, calcium for improving the castability, magnesium for increasing the corrosion resistance, and at least one metal of the iron group, or silicon, for improving the strength of the alloys .under high temperature conditions, and for increasing the yield point. Such, and other, alloying elements are usual in magnesium alloys, and they do not affect the properties of our novel alloys.

Examples oi suitable alloys according to our It is understood that in all cases the remainder is substantially all magnesium.

As mentioned, the third element in our alloys isat least one metal of the group including bismuth, lead, and tin. Further investigations have shown that bismuth in our alloys can be replaced entirely or partly by lead or tin, or by lead plus tin. For instance, in the alloy No. 4 the 8% bismuth can be selectively replaced by either 8% or lead, or. 8% of tin, or by 4% of lead and 4% of tin; or by 6% of lead and 2% of tin, etc. If it is desired to replace the bismuth only partly,

the said alloy No.4 may contain 3% of bismuth and 5% of lead, or 3% of bismuth and 5% obtain, or 3% of bismuth and 2% oilead plus 3% of tin, or 3% of bismuth and 4% of lead plus 1% of tin, etc. The strength and other mechanical properties of the alloys are aflected by such variations only to a negligible extent.

Under all conditions, however, the total of the alloying elements must not be less than 6%, and not more than 23%.

We claim:

l. A magnesium alloy containing from 1 to 15 per cent of aluminium; from 1 to 15 per cent of cadmium and from 1 to 15 per cent of at least one metal selected from the group consisting of bismuth, lead and tin, the total content of said alloying elements being from 6 to 23 per cent, the remainder being substantially all magnesium.

2. A magnesium alloy containing irom 1 to 15 per cent of aluminium, from 1 .to 15 per cent of cadmium and from 1 to 15 per cent of bismuth, the total content of said alloying elements being from 6 to 23 per cent, and the remainder being substantially all magnesium.

ARTHUR BURKHARDT. RICHARD KNABE.

CAD 

